It has previously been proposed to determine whether one or more wheels of a vehicle are no longer in contact with the ground. U.S. Pat. No. 6,904,350 discloses an arrangement in which the signals from inertial sensors are used to make a determination as to whether two wheels on the same side of a vehicle have lost contact with the ground, to assist in the early detection of a roll-over situation. US publication 2007/0185623 discloses an arrangement in which suspension sensors are provided, to gauge from the behaviour of the suspension systems associated with a vehicle's wheels whether the wheels are still in contact with the ground. This document is also concerned with the detection of roll-over situations.
It is an object of the present invention to provide an improved vehicle safety system of this type.